Hereinafter, a single-carrier and multi-carrier modulation scheme used in the embodiments of the present invention will be briefly described.
A Single-Carrier Modulation (SCM) scheme refers to a modulation scheme for performing modulation by carrying all information on one carrier, unlike a Multi-Carrier Modulation (MCM) scheme.
The SCM scheme is weak against frequency selective fading. Accordingly, in order to overcome the frequency selective fading, a complicated equalizer is necessary. In addition, if the SCM scheme is used, a protective band or the like is necessary and thus band efficiency is bad.
The MCM scheme refers to a technology of dividing an overall bandwidth channel into several sub-channels each having a small bandwidth and transmitting a plurality of narrowband sub-carriers through the sub-channels.
In the MCM scheme, each of the sub-channels is approximated so as to have a flat channel due to the small bandwidth. The MCM scheme can compensate for distortion of a channel using a simple equalizer. In addition, the MCM scheme is implemented at a high speed using Fast Fourier Transform (FFT) and is more advantageous in high-speed data transmission than the SCM scheme.
Hereinafter, an idle mode of a mobile station and a paging group related to the embodiments of the present invention will be briefly described.
The idle mode generally refers to an operation for enabling downlink (DL) broadcast traffic reception to be periodically performed although a mobile station is not registered in a specific base station, when the mobile station is moved in a radio link environment including multiple base stations.
If a mobile station does not receive traffic from a base station during a predetermined time, the mobile station may transition to the idle mode in order to save power. The mobile station which transitions to the idle mode may receive a broadcast message (e.g., a paging message) transmitted by the base station during an available interval and determine whether the mobile station transitions to a normal mode or is in the idle mode. In addition, the mobile station which is in the idle mode performs location update so as to inform a paging controller of its location.
The idle mode may eliminate demands for activation associated with handover and demands for a general operation so as to provide benefits to a mobile station. The idle mode may restrict the activity of a mobile station to be scanned in a discrete period so as to reduce power consumption and operational resources used by the mobile station.
In addition, the idle mode may provide a simple appropriate scheme for informing a mobile station of pending DL traffic, and eliminate radio interface and network handover (HO) traffic from an inactive mobile station so as to provide benefits to a network and a base station.
Paging refers to a function for recognizing the location (e.g., any base station or any mobile switching center) of a Mobile Station (MS) when an incoming signal is occurred in mobile communication. A plurality of Base Stations (BSs) for supporting the idle mode may be included in a specific paging group so as to configure a paging area.
At this time, the paging group indicates a logical group. The paging group is used to provide a neighbor area which may be paged in DL if there is traffic which targets an MS. It is preferable that the size of the paging group be large enough to enable a specific mobile station to be located in the same paging group during the most time, and small enough to enable a paging load to be held at an appropriate level.
The paging group may include at least one BS. One BS may be included in one or more paging groups. The paging group is defined in a management system. In the paging group, a paging-group-action backbone network message may be used. In addition, a paging controller may manage a list of mobile stations, which are in the idle mode, using a paging-announce message which is one of backbone messages, and manage initial paging of all BSs belonging to the paging group.
The coverage of a mobile station which enters the idle mode becomes a BS paging group which is a group of multiple BSs. That is, a mobile station which is in the idle mode may belong to at least one of geometrically separated BS paging groups. In addition, a base station may recognize the location of an idle-mode mobile station in a unit of a paging group only, although the idle-mode mobile station does not receive a service from the base station. Accordingly, the base station should broadcast a paging message to mobile stations in all paging intervals which are set with respect to the idle-mode mobile stations belonging to its paging group. At this time, when the base station belongs to one paging group and supports multiple carriers, all the carriers supported by the base station have the same paging group ID.